Soybean Cyst Nematode Continues to Spread

Although I have talked about Soybean Cyst Nematode management in the past, the spread of this pest over the past few years requires an update.

One year ago, I talked about a SCN joint project between NDSU and the ND Soybean Council utilizing Agvise Labs to test the majority of the soil samples. The project revealed a total of twelve ND counties, from Emmons to Pembina, where soils tested positive for SCN. In 2010 only 28.9% of the samples from the five southeastern ND counties tested positive. Test results in these same counties increased to 37.7% in 2011 and to a whopping 54% in 2012. Keep in mind that these samples were submitted specifically to test for SCN. But positive samples nearly doubling over two years proves the increased spread of this pest.

The egg count numbers reported by Agvise have been extremely high in these new SCN areas. Test results of 200-2,000 eggs per 100 ccs, generally include a recommendation to plant a resistant variety. With an egg count of 2,000-4,999 per 100 ccs, a resistant SCN variety would likely struggle, and with a count over 5,000 eggs per 100 ccs, a non-host crop should be planted.

Here is an example from Agvise’s website (http://www.agvise.com/soil-test-summaries/). A sample from Clay County, MN shows an egg count of 396,000, and a sample from Cass County, ND shows a count of 129,000. Since it takes ten years of planting a non-host crop to reduce the levels by 10,000, you can imagine how long it will take before a successful soybean crop will grow in these fields.

It is easy to understand why we, as a seed company, are searching for additional products with SCN resistance, without giving up yield or agronomic characteristics like excellent IDC tolerance.

SCN needs to be understood to be managed. SCN is a microscopic roundworm that penetrates the roots of the soybean. The females stay on the roots and swell into the lemon-shaped cysts that are visible. These cysts each contain 250-500 eggs which can either burst, releasing the eggs to infect other roots or remain dormant for many years. SCN harms soybean yields by robbing nutrients and water from the plant. Yield is affected before visual symptoms are noticed. That is why it is so important for us, in this region where the presence of SCN is growing, to scout our fields this summer to identify the problem before it robs yield.

If you suspect SCN was present in any of your fields last year, be sure to test this summer. You may also want to include a SCN resistant variety in your seed plan for 2013. You can either use the resistant variety across the entire field or if you use a row planter, add 2-4 rows of SCN beans. This is a good way to see if resistance is present on your farm.

Call your local seed dealer or county agent for more information.

Adam Spelhaug is the Agronomy Manager at Peterson Farms Seed, and writes a monthly column in the Dakota Farmer.